speech

speech is a poor signal to noise

overcoming the poor signal-phonemic restoration effect

  • context allows brain to predict what phoneme should have been there and makes you actually hear it-fires that phoneme detector-only works when the noise would have masked the phoneme

how do we know it actually fires the phoneme detector?

  • run a study w ambiguous sound (dime/time ex.)

  • Adapt to “Tony the Tiger” or “Tony the *ger” or “Tony the _ger” (where * is cough / is blank).

  • If cough the missing phoneme adapts (Samuel, ’81)

aids help disambiguate phonemes

  • visual input

    • McGurk effect: people integrate what they see the mouth do with the sound that hits the ears

    • dubbing experiments

      • voice says “ba” and lips go “ga”, people hear “da”

• Lip movement for “ga” – similar (visual) movement to “da” not “ba”

• In terms of sound “ba” is more similar to “da” than “ga”.

• So, brain takes the “best” choice and you hear “da” – sound that is close to what is heard and matches lip movement -

  • easier to understand speaker when you can see them talk

  • gestures also help - congenitally blind people gesture

parsing phonemes is difficult

  • coarticulation

    • allows for super fast speaking - but means we blend language together

    • listening to spoken language is like reading text where the words overlap

  • ex. hearing unfamiliar language - seems like no break between words

  • if look at sonogram of our speech there are no breads between words - brain inserts breaks

how?

  • top down influences

  • knowledge of structural rules/statistical regularities (ex. words can end but not begin with “RK”

context influences how we perceive phonemes

  • ex. words in and out of sentence

  • much easier to identify words in sentences

    • ex. pollack and picket - tapes Ss in waiting room, then isolated single words and played them back

    • people could not identify 50% of their own words

two influences of context

  • semantic context allows brain to constrain appropriate words

  • speech context (how speaker talks) allows brain to undo effects of coarticulation

Top down influences on speech perception

  •  Context & Expectation have large effects-

  •  Our brains parse information into meaningful parts and insert breaks where there are none

  •  phonetic restoration -

  •  our brains reinsert information that is masked, so we still hear it

problems w understanding a sentence:assuming you can get the right words…how do you extract the right meaning?

  • ex. he made her duck

  • surface structure - the words on the page

  • deep structure - the meaning (semantics)

  • same surface structures can have multiple deep structures

context deals with ambiguity

speech is not a great signal, but we have developed many ways to constrain interpretations to help disambiguate